Unraveling the Genetic Code: Exploring the Secrets of DNA

Unraveling the Genetic Code

Exploring the Secrets of DNA

Multiple Choice

Where does DNA replication occur in eukaryotic cells?

• Nucleus

• Cytoplasm

• Cell Membrane

• Mitochondria

Multiple Choice

What is the function of helicase in DNA replication?

• Gluing DNA fragments together

• Building new DNA strands

• Unzipping the DNA strands

• Making RNA primers

Multiple Choice

What is the role of primase in DNA replication?

• Gluing DNA fragments together

• Unzipping the DNA strands

• Building new DNA strands

• Making RNA primers

Multiple Choice

Which direction does DNA polymerase build the new strand?

• Both directions

• Random direction

• 3' to 5'

• 5' to 3'

Multiple Choice

What is the purpose of ligase in DNA replication?

• Gluing DNA fragments together

• Making RNA primers

• Building new DNA strands

• Unzipping the DNA strands

DNA History

• In 1869, a molecule called 'nuclein' was isolated from a cell nucleus.

• It was later identified as a nucleic acid.

• Five nitrogen bases (A, C, G, T/U) were identified as the building blocks of DNA and RNA.

• Chromosomes were discovered, and it was found that they double during inheritance.

History of DNA

In the 1940’s Scientist  E. Chargaff discovered that DNA is responsible for heredity and that it varies between species. His discoveries, known as Chargaff’s Rules, proved that guanine and cytosine units, as well as adenine and thymine units, were the same in double-stranded DNA, and he also discovered that DNA varies among species. His work was used to support such findings that genes can move on a chromosome.

1951 — Rosalind Franklin’s X-ray diffraction photographs of DNA showed the helical form. (Her findings were only acknowledged posthumously)

Watson and Crick confirmed Franklin’s helical model of DNA  and built a  working model of DNA. They are credited to discovering the double helix structure of DNA.

Multiple Choice

What was the molecule called 'nuclein' later identified as?

• Protein

• Carbohydrate

• Lipid

• Nucleic acid

Multiple Choice

Who discovered the double helix structure of DNA?

• James Watson

• Francis Crick

• Rosalind Franklin

• Gregor Mendel

DNA Structure: Double Helix Discovery

• DNA is made up of repeating monomers called nucleotides.

• DNA is in the shape of a double helix. 

• The sugar in DNA is called deoxyribose. The backbone is made up of alternating sugars and phosphate groups. 

• The rungs that make up the middle of the DNA model are made up of complementary nitrogenous bases. 

• The nitrogenous bases include:

  • Purines - Double ring 

    • Adenine

    • Guanine

  •  Pyrimidines - single ring 

    • Thymine

    • Cytosine

DNA Function

• DNA is the information molecule. It stores instructions for making other large molecules, called proteins. 

• The instructions for the proteins are stored inside each of your cells, distributed among 46 chromosomes (human).

•  These chromosomes are made up of thousands of shorter segments of DNA, called genes. Each gene stores the directions for making protein fragments, whole proteins, or multiple specific proteins.

DNA Function

• As the nucleotide sequence begins to grow, according the base pair rules, the following is applied. 

  • C and G pair together 

  • T and A pair together

  How do the nitrogenous bases stick together? 

  Hydrogen bonds

  • 3 H bonds hold G & C together

  • 2 H bonds hold T & A together

Multiple Choice

What is the function of DNA?

• DNA stores instructions for making proteins in cells.

• DNA replicates during the S phase of interphase.

• DNA polymerase attaches new nucleotides during elongation.

• Helicase breaks hydrogen bonds during initiation.

DNA Replication

• DNA Function: DNA stores instructions for making proteins in cells.

• DNA Replication: DNA replicates during the S phase of interphase, making an exact copy of the instructions

• Step 1: Initiation: Helicase breaks hydrogen bonds, creating a replication fork.

• Step 2: Elongation: DNA polymerase attaches new nucleotides, following complementary base pairing. (Chargaff's Rule)

• Step 3: Termination: An enzyme ligase, glues together the bases with hydrogen bonds. 

DNA Replication

• DNA Function: DNA stores instructions for making proteins in cells.

• DNA Replication: DNA replicates during the S phase of interphase, making an exact copy of the instructions

• Step 3: Termination: An enzyme ligase, glues together the bases with hydrogen bonds. 

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Enzyme Ligase

Trivia: Enzyme ligase is responsible for gluing DNA strands together during DNA replication. It plays a crucial role in the formation of a complete and functional DNA molecule. Without enzyme ligase, DNA replication would not be possible.

Unraveling the Genetic Code

Key Concepts:
- DNA replication is a semi-conservative process
- Chargaff's rule: A pairs with T, G pairs with C
- Enzyme ligase glues DNA strands together
- DNA structure: sides made of sugar-phosphate backbone, rungs made of nitrogenous bases

Multiple Choice

Which enzyme is responsible for gluing DNA strands together?

• DNA replication

• Chargaff's rule

• Enzyme ligase

• DNA structure